Add MLTuple, SVD, ALS

[jey]

This PR makes three main changes:

1. Reorganizes the MLRow and MLVector types into a new MLTuple-based hierarchy
2. Adds randomized truncated SVD
3. Adds Alternating Least Squares (ALS)

Caveats:

1. Documentation is forthcoming
2. There's a few FIXMEs scattered about still (especially in dealing with schema modification, e.g. setColName)
3. Currently requires a special build of jblas for the QR decomposition, we could switch to using SVD, or we can bundle our own build of jblas inside MLI